Fire control system for use in conjunction with electronic image motion stabilization systems

ABSTRACT

An image motion stabilization system for eliminating motion of an image being viewed from an unstable support. The image is viewed through an image converter tube. X and Y rate gyroscopes are mounted on the unstable support to sense motions of the support, and the outputs from the gyroscopes are applied to the deflection coils of the converter tube to compensate for movements of the support. Panning control means are provided to prevent image deflection in the converter tube to allow panning when the support is moved at a slow rate. Embodiments of the invention are disclosed wherein the image motion stabilization system is utilized with a camera or in a fire control system. In the fire control system embodiment a circuit is provided to sense when the weapon is correctly aimed, and to automatically fire the weapon in the correctly aimed position.

United States Patent Philbrick et a1.

451 May 2, 1972 [72} Inventors: Richard W. Philbrick, Concord; Eh'aim R.

Arazi, Cambridge, both of Mass.

[52] U.S. Cl. ..89/28, 89/41 8, 89/41 E, 89/41 ME, 89/41 1..

[51] Int. Cl. ..F4lc 19/12, F41f 13/08 [58] Field of Search ..42/84;89/28, 41, 41.1, 41.2, 89/41.5, 41.6, 41.61, 41.62, 41.76, 41.7 ME,41.71,

[56] References Cited UNITED STATES PATENTS 1,288,386 12/1918 Conill..89/41.7 L UX 2,359,032 9/1944 Gott .89/41.7 ME UX 2,394,021 2/1946Stone ..89/4l.8 UX

IMAGE lNTENSlFlER SECTION 27 RIFLE BORE 2,434,654 1/1948 Watkinsetal...s9/41.2x 2,705,371 4/1955 Hammond ..89/41.6X 2,869,803 1/1959 M6066l78/DIG.I 3,212,420 10/1965 Cievra... ..95/12.5 3,293,360 12/1966 Smith..l78/6.8 2,306,972 12/1942 Mfiisel 89/4L1UX 2,660,794 12/19536081128181.. .....89/41.6X 3,169,191 2/1965 Knapp ..s9/41.1ux

Primary ExaminerBenjamin A. Borchelt Assistant Examiner-Stephen C.Bentley AnomeyHomer 0. Blair and Robert L. Nathan [57] ABSTRACT An imagemotion stabilization system for eliminating motion of an image beingviewed from an unstable support. The image is viewed through an imageconverter tube. X and Y rate gyroscopes are mounted on the unstablesupport to sense motions of the support, and the outputs from thegyroscopes are applied to the deflection coils of the converter tube tocompensate for movements of the support. Panning control means areprovided to prevent image deflection in the converter tube to allowpanning when the support is moved at a slow rate. Embodiments of theinvention are disclosed wherein the image motion stabilization system isutilized with a camera or in a fire control system. In the fire controlsystem embodiment a circuit is provided to sense when the weapon iscorrectly aimed, and to automatically fire the weapon in the correctlyaimed position.

12 Claims, 12 Drawing Figures OCULAR 2B GYRO cuzcun fi/ COOLING FlNS 31DEFLECTION SYSTEM HOUSING 29 Patented May 2, 1972 3,659,494

4 Sheets-Sheet 1 FIG. I (2 HAND HELD CAMERA] PHOS HOR 19 4 I6 f X H 14\TARGETSCREENA Y 17 GY Ro J GYRO CIR UIT S CIRCUIT X &EJ' -v DEFLECTIONCOIL fly IMAGE CONVERTERA PHOTOEMISSIVE 3 SCREENII "TO INTEGRATINGOCULAR 28 AMPLIFIER OF FIG] IMAGE INTENSIFIER SECTION 27 TELE SCOPIC 3OBJECTIVE 2b COOLING FINS 31 DEFLECTION SYSTEM HOUSING 29 INVENTOR.

Patented May 2, 1972 3,659,494

4 Sheets-Sheet 2 r59 VARIABLE SLOPE i 1 SAWTOOTH GENERATOR kifi" VEHICLEFRAME E FIG. .5

V/ H COMPUTER VARIABLE SLOPE SAWTOOTH GENERATOR ADDER X- DIRECTION 39 7X-DIRECTION 56 5 Y-DIRECTION FREE GYRO63 FREE GYRO 54 47 p43 L- 6 34 4333 34 48 kg? AIRCRAFT FRAME 32 li\\ RATE GYRO -w' TO X-DEFLECTIONINVENTOR.

V COIL Patented May 2, 1972 4 Sheets-Sheet 3 2650i O-E m h mmOOE 3:316@25; zocuwmak INVENTOR.

Patented May 2, 1972 3,659,494

4 Sheets-Shoat 4 V OUT TRIGGER 7 2 v INTEG. OUTPUT --I=IRING RANGE F/G.9 ea TRIGGER AMPLIFIER N AND 96 Im 88 OUTPUT I 2 GATE OUTPUT TO GRouNDON OFF MARK TRIGGER 7 POSITIVE oN oN NO MARK 93 INHIBIT DISABLE NEGATIVEOFF OFF NO MARK 7 SW'TCH ONE SHOT E /MuLTIvIBRAToRao F/G. I0 87 88 2I'To FIG 7 x-RATE 5 GYRO ,84 -92 NEGATIvE 3 INTEGRATING AMPLIFIERMULTIVIBRATOR a9 cAMERA SUPPORT CASE III GYRO CIRCUIT N FIG.2

INTEGRATIN RETURN BEAM I08 AMPLIFIER I6 SCANNING BEAM I07 IMAGE ORTHICONCAMERA SECONDARY EMISSION TUBE I02 TARGET SCREEN I04 COLLECTING SCREENI06 INVENTOR.

FIRE CONTROL SYSTEM FOR USE IN CONJUNCTION WITH ELECTRONIC IMAGE MOTIONSTABILIZATION SYSTEMS This patent application is a division of patentapplication Ser. No. 462,322, filed June 8, 1965, now U. S. Pat. No.3,515,881, issued June 2, 1970.

The present invention relates to devices for stabilizing an opticalimage in a field of view. More particularly the present inventionrelates to an image motion cancellation viewing system for cancellingapparent image motion of viewed images.

In a copending application assigned to a common assignee entitled DataPattern Motion Cancellation System, filed Aug. 7, 1964, Ser. No.388,251, invented by Efraim R. Arazi, an image motion cancellationsystem is disclosed. In that application the broad environment for theproblem of image motion is outlined. The system described in thecopending application is limited in certain applications. For nightphotography, for example, and other dimly lighted environments, thelight intensity may be too low for the light sensors to operateeffectively. For applications involving images which are not sharplydefined and for rapidly changing scenes, the system disclosed in thecopending application is sometimes unable to lock on a desired image.

It is often desirable to photograph or telescopically view objects frommoving vehicles such as automobiles, helicopters, trains, planes, boatsand space vehicles. However the motion of these vehicles causes theviewed objects to dance so that it is often very difficult or impossibleto discern, photograph, or televise details of the viewed objects. Theproblem is compounded when the objects are moving and the observer musttrack the moving object with an optical instrument. Also under theseconditions observer fatigue can be quite severe. Generally speaking, thesharpness of a picture is determined by the smallest element in it thatcan independently represent a certain number of gray shades particularlyin pictures taken with a short exposure time. The relatively few exposedgrains and the randomness of the grain distribution in each element makeit difficult to achieve a sufficiently high signal to noise ratio perelement. Therefore, longer exposure may be desirable. However is cameramotion occurs during the longer exposure period, the resulting dance orblur limits the smallest element that can have an independent number ofgray shades. Accordingly, the need for a system to freeze" the image andthereby eliminate the image dance" is readily apparent in numerous areassuch as series reconnaissance, television, map making, the militaryfield in general, motion picture making, and in the field of photographyin general.

Regarding aerial reconnaissance, one approach to this problem is todetect pitch" and yaw of an aircraft (and hence a camera mount) byvirtue of electrical transducers and utilize the signals generatedthereby to actuate servo systems coupled to the camera mount orcounteract the pitch" and yaw." Such an approach is obviously cumbersomeand expensive since many pounds of equipment must be mechanicallyactuated. Also image dance in a telescopic gunsight presents obviousproblems.

It is, therefore, an object of the present invention to provide a newand improved image motion cancellation system.

It is a further object of the present invention to provide a new andimproved image motion cancellation system which may operate upon animage having relatively low light intensi- It is a further object of thepresent invention to provide an image motion cancellation system whichmay operate upon images which are not sharply defined or which lackclarity.

It is yet a further object of the present invention to provide an imagemotion cancellation system particularly useful in aerial photography foreliminating intentional film motion, within each take or frame period,utilized in the prior art to provide image motion cancellation inaccordance with the Y/Hratio.

It is yet a further object of the present invention to provide a camerawhich may clearly and distinctly photograph objects although the cameraitself may be wildly gyrating.

It is yet a further object of the present invention to provide opticalviewing instruments such as cameras, telescopes, binoculars, gunsights,and television pickup tubes which eliminate "dance" due to randommotions of the viewing instruments, due to the fact that they are handheld, vehicle mounted, or otherwise.

It is yet a further object of the present invention to provide a uniquefire control system.

Further objects of the present invention will be apparent from thefollowing description taken in conjunction with the following drawingsin which:

FIG. 1 discloses a hand held camera built in accordance with the presentinvention.

FIG. 2 discloses the gyro circuit of FIG. 1.

FIG. 3 discloses a telescope or gunsight built in accordance with thepresent invention.

FIGS. 4 and 5 disclose embodiments of the present invention which haveparticular applicability to serial reconnaissance photography.

FIG. 6 discloses an integrator circuit utilized in conjunction with theembodiments of the invention.

FIG. 7 discloses electronic circuitry utilized in a novel fire controlsystem embodying the present invention.

FIG. 8 discloses a graph illustrating the operation of the triggeramplifiers of FIG. 7.

FIG. 9 discloses a logic table illustrating the operation of the firingcircuits.

FIG. 10 discloses a weapon velocity inhibit circuit.

FIG. 11 discloses a trigger pressure inhibit circuit.

FIG. 12 discloses an embodiment of the present invention utilized in thetelevision field.

In accordance with the present invention an optical viewing means ispositioned upon a support member such as the frame of a vehicle, weapon,or a camera case along with imaging means which generally include anobjective lens and an image converter or intensifier which focuses theimage of the viewed object at the viewing means. Random motions of thesupport member which cause the aforesaid image dance" are converted intoX and Y electrical signals proportional to the direction and degree ofdance. These signals are applied to a deflecting system which causes theelectron image bundle generated within the image converter to bedeflected by an amount and in a direction to cancel that image motionwhich would otherwise occur due to motions of the support member in theabsence of the deflecting system.

FIG. I discloses a camera 1, which could be handheld, having a lighttight case 2 and an objective lens 3, positioned at one end of the case,as shown. An image converter or intensifier tube 4, focusing lens 5, andfilm 6 are positioned as shown. Film 6 is positioned within focal plane8 and is supported and actuated by rollers 9. Image converter tube 4 andfocusing lens 5 are, of course, afiixed to case 2.

A scene to be photographed is imaged upon photoemissive screen 11 bylens 3. As photons strike the photoemissive screen 11, coated on theinside of the evacuated envelope of the image converter, severalelectrons are emitted for each photon. Focusing and acceleratingelectrodes, not shown, but contained within image converter 4, cause theelectron bundle composed of a number of electron streams to be focusedupon phosphor target screen 12. Since the intensity of the electronstreams emitted by incremental areas of the photoemissive screen areproportional to the intensity of light falling upon these incrementalareas, it follows that the total electron bundle making up the numerouselectron streams, represent the viewed scene, and will be reconvertedinto an optical image by the phosphor target screen 12. In the preferredembodiment of the present invention, the optical image focused uponscreen 11 will be amplified owing to the acceleration of the electronstreams within the image converter or image intensifier 4. However theimage need not necessarily be amplified. For a discussion of varioustypes of image converters see Van Nostrands Scientific Encylopedia,third edition, January, 1958, page 860.

An X direction rate gyro circuit 13 is electrically coupled to magneticdeflection yoke 14, which is associated with image converter 4, throughintegrating amplifier 16. Likewise Y direction rate gyro circuit 17 iscoupled to Y direction magnetic deflection yoke 18 through integratingamplifier 19.

Gyro circuits l3 and 17 are well known to those skilled in the art. FIG.2 schematically discloses the major components of gyro circuits l3 and17, however.

It should be appreciated at this point that the aforesaid image motionor dance," which is to be cancelled out by the present invention, is dueprimarily to angular motion of camera 1 about optical axis 7. Asmentioned hereinbefore, the angular X and Y direction motions of camera1 are detected by transducer means associated with the camera and causeelectrical fields to be set up within image converter 4 in a directionand by an amount to cancel the dance" effect which would otherwise beproduced in the absence of the deflecting means. Accordingly, the gyrocircuits l3 and 17 together with their associated integrating amplifiers16 and 19 cause currents to pass through yokes l4 and 18 proportional toangular displacement of the camera axis. X direction rate gyro 21 ofFIG. 2 is supplied with a 400 cycle, 26 volt, carrier signal produced byAC generator 22. The output of the gyro is applied to a phase sensitivedetector 23 via amplifier 24. The phase sensitive detector 23 is alsosupplied with a reference signal which is the same as that signalapplied by AC source 22 to rate gyro 21. The amplitude modulated carrierapplied to phase sensitive detector 23 by the rate gyro will beamplitude modulated in accordance with the instantaneous angularvelocity of the camera with respect to the gyro axis. The direction ofthe angular velocity will be indicated by the relative phase of the AMcarrier produced by rate gyro 21 with respect to the reference signalapplied to detector 23. In other words as the angular velocity of thegyro increases in a first direction with respect to the camera case 2,the amplitude of the low frequency detected signal increases and has apositive polarity. Where this angular velocity decreases in the firstdirection the amplitude of the detected signal decreases but is stillpositive. On the other hand if the angular velocity direction isreversed, a negative signal will be produced by detector 23, theamplitude of which is proportional to the instantaneous angular velocityof the gyro with respect to case 2. Accordingly, it should beappreciated that the output of detector 23 produces an AC voltage waveshape which represents instantaneous angular velocity against time,which wave shape which will be both positive and negative depending onthe instantaneous direction of the angular velocity of motion of thecase with respect to the gyro axis. As is also well known to thoseskilled in the art, the integration of such a wave shape produces a waveshape which represents the instantaneous position of the case withrespect to the gyro axis both to the left and to the right of the nullposition. Accordingly, it should be understood that the instantaneousposition of the camera case about a null, home" or on target positionwill cause an electrical field to be set up within image converter 4proportional to such deviation. Thus the electron image within theconverter becomes frozen. Of course, the Y direction gyro circuit 17would be identical with X gyro circuit 13, so that the composite pitch"and yaw deviations of the camera case about the target" viewing positionwill enable image motion or dance" to be completely cancelled out. Theresulting photos taken by the inventors have been clear and distinctwhere they would otherwise have been smeared beyond recognition.

It should be understood that, if desired, electrostatic deflectionplates may be utilized in image converter or image intensifier 4 inplace of the magnetic deflection yokes. However the use of magneticdeflection yokes are preferable in view of the elimination of highvoltage power supplies. It should also be understood that although inthe preferred embodiment image converter 4 will act as an optical imageintensifier, light amplification by means of the operation of imageconverter 4 is not essential where the scene to be viewed issufficiently bright. The actual image tube utilized in one camera builtby the inventors was an RCA C33004B (development type) tube. The yokeswere produced by Syntronics Instruments Incorporated model numberC3440Yl9580. The gyro was a U. 5. time model 60 while the amplifierswere Philbrick P65/A operational amplifiers.

A terrestrial telescope was built by the inventors in accordance withthe present invention and is schematically shown in FIG. 3. Thetelescope comprises telescopic objective 26, image converter orintensifier section 27, ocular 28 and the deflection system housing 29which includes the gyroscopes. Cooling fins 31 were formed on theoutside of housing 29 in order to provide for gyroscope cooling. Owingto telescopic objective 26, distant objects are viewed by the telescopeand, therefore, it should be apparent that slight motions of thetelescope will cause the image viewed by the observer by means of ocular28 to dance about. A telescope manufactured in accordance with thepresent invention will eliminate this dance" so that details of thedistant scene which is viewed by the telescope may be rapidly andreadily discerned without the accompanying operator fatigue which occursthrough the use of standard telescopes. The telescopic objective 26focuses the distant scene upon the photo-emissive screen of the imageintensifier tube and the ocular 28 focuses the image produced by thephosphor target screen at the retina of the observer or in thealternative at a photographic plate. This embodiment is otherwisesimilar to FIG. 1.

FIGS. 4 and 5 schematically disclose aerial cameras which embody thepresent invention. As mentioned hereinbefore. the use of highlystabilized platforms to prevent camera motion owing to pitch and yaw" ofan aircraft are extremely expensive, cumbersome, and complex.

In FIG. 5 the frame or body of the aircraft 32 supports platform 33 bymeans of shock mounts 34 which prevent high frequency vibrations of theaircraft frame 32 (i.e. frequencies above 40-60 cycles per second) fromvibrating the image intensifier or camera element relative to each otheror otherwise. Camera 36 is schematically shown rigidly mounted uponplatform 33 by means of struts 37 and 38. Likewise image intensifier 39is rigidly aflixed to platform 33 by means of struts 41 and 42. Itshould be appreciated that platform 33 together with aircraft frame 32form a composite support member for the camera system. Objective lens 43is schematically shown mounted within the support platform and focusesthe scene to be photographed on the photo-emissive screen of imageconverter 39 in the embodiment of FIG. 1. The optical image produced bythe phosphor target screen of image converter 39 is likewise focusedupon film 44 by means of lens 46. The flight path of the aircraft isschematically represented by arrow 47 while the pitch" of the aircraftis represented schematically by arrows 48 and 49. In this embodiment thepitch" of the aircraft will be termed the X direction camera supportdeviation, while the yaw" of the aircraft will be represented by the Ydirection angular deviation. It should now be understood that for agiven frame or (take) the pitching and yawing" will cause a certaindegree of image smear so that resolution is thereby degragated. Inaccordance with the present invention these effects of pitch and yaw"upon the image produced at the camera focal plane is cancelled out, justas the image motion due to the aforementioned cameras and telescopemotions are cancelled out.

In these embodiments free gyros are utilized rather than rate gyros, sothat the integration amplifiers discussed hereinbefore may be omitted.However it should be understood that rate gyros together with theirassociated integrating amplifiers on accelerometers together with theirassociated double integrating amplifiers may also be utilized.

The output circuit of X direction free gyro 63 is electrically coupledto the X direction magnetic deflection coil 51 via adder 52 andamplifier 53. In view of the previous description of the embodiment ofFIG. 1, it should be apparent that image motion or dance" at film 44 dueto the pitching of the aircraft will be effectively cancelled out bymeans of magnetic deflection coil 51. Likewise image motion due to theyaw of the aircraft is cancelled out by means of Y direction free gyro54 which is coupled to Y direction magnetic deflection yoke 56 viaamplifier 57. Thus the up" and down pitch motion of the aircraft willcause currents to flow through the X direction magnetic deflection coil51 in a direction depending upon whether the instantaneous pitch is "upor down" and in an amount depending upon the degree of said deviation.Likewise "left" and right" yaw deviations will cause currents to flow inopposite directions through deflection coil 56 and in an amountdepending upon the degree of said yaw.

The purpose of adder 52 will become apparent upon the inspection of FIG.4. The flight of the aircraft is schematically disclosed by arrow 58. Asis well known to those skilled in the art of aerial reconnaissance,there will be an apparent image motion at the camera focal plane owingto the forward motion of the aircraft, the degree of this image motionbeing proportional to the well known V/l-I ratio, where V is therelative velocity of the aircraft with respect to the ground where theground is being photographed, and H is the altitude of the aircraft. Itshould be apparent that the higher the velocity of the aircraft withrespect to the ground scene being photographed the greater the apparentimage motion at the camera focal point. On the other hand, the greaterthe altitude the aircraft with respect to the ground scene the less thedegree of apparent image motion at the focal plane of the camera. In theprior art the V/l-I ratio is determined, and from that determination thefilm is intentionally moved during each take an amount proportionalthereto, so that the film chases the moving image at the camera focalplane and as a result smear is considerably reduced and resolution isgreatly improved. This intentional film motion within a given frame ortake" has been eliminated by the inventors by means of applying asawtooth wave form to the X direction magnetic deflection coil 51' andconsequently intermittent film motion during a given frame or take" isno longer needed. In the absence of the application of a sawtooth waveto magnetic deflection coil 51', the image would move to the right onfilm 58. However, the increasing magnetic field produced by the sawtoothwave applied to deflection coil 51 will freeze" the image so that thereis no apparent image motion with respect to the camera focal plane,thereby to eliminate the complex mechanism for moving the film during agiven frame. The output circuit of variable slope sawtooth generator 59is coupled to X direction magnetic deflection coil 51 through amplifier61, as shown in FIG. 4. As is well known to those skilled in the art,the slope of the wave form produced by sawtooth generator 59 may bevaried by varying the value of the capacitor or resistor in the RCcircuit of the generator, V/I-I computer 62, therefore, will vary thetime constant of the RC timing circuit within the sawtooth generator inproportion to the computed V/H ratio, to alter the slope of the waveform and hence the degree of image motion cancellation as required bythe particular V/H ratio.

It is often desirable to optically freeze" a viewed portion of an itemmounted upon a shaker table, which is used to vibrate the item mountedthereon in a known mode, such as a sinusoidal mode. One method offreezing the viewed portion would involve the use of a stroboscope,which produces an intense light flash having a very short durationrelative to the vibrational period of the table, which flash issynchronized with the frequency of vibration of the shaker table.However, if the flash frequency is not quite synchronized with theshaker table frequency, which is often the case, the viewed portion ofthe item on the table will appear to slowly move, or drift, which ofcourse is undesirable. Another method of accomplishing the foregoing isto utilize the system disclosed in the aforesaid Arazi application. Athird method is available utilizing the teachings of the presentinvention. The image motion of the viewed portion of the item mountedupon the shaker table is generally known and controlled so thattransducer means may be mounted upon the table or upon the table driveshaft to produce electrical signals proportional to the instantaneousposition of the table. For example, where the table vibrational mode issinusoidal, an AC generator may be driven by the table drive shaft andthe signals produced thereby would be applied to the deflection coils ofthe image intensifier in a manner to freeze" the image in accordancewith the aforesaid teachings of the present invention. Should the tableor base support member of the viewed item have a vibrational mode whichis not predetermined, a transducer may be mounted upon the table therebyto produce an electrical signal proportional to the displacement of thetable, against time, as in the foregoing embodiments.

In a high speed motion picture camera, where the film is continuouslydriven through its focal plane at high speed, a prism is rotated tocause the image to chase" the film, thereby to eliminate relative motionbetween the image and the film, to in turn produce a distinct picture.Since the film motion rate is known, it may be seen that the rotatingprism may be replaced by the stationary image converter whose deflectioncoils are supplied by current from a signal generator proportional tothe instantaneous displacement of the moving film from a starting datumduring a given "take", all in accordance with the teachings of thepresent invention. Of course, if electrostatic plates are utilized aspart of the image intensifier deflection means, a high voltage would beapplied to the plates proportional to the film displacement from thestarting datum position.

In FIG. 5 VIII analog computer 62' is connected to variable slopesawtooth generator 59 in accordance with the discussed arrangement ofFIG. 4. The output circuit of sawtooth generator 59 is applied to afirst input terminal of analog adder 52, while the output circuit of Xdirection free gyro 63 is coupled to the second input terminal of adder52. Since the apparent image motion at the camera focal plane is afunction of both the random pitch" of the aircraft and the aforesaid V/Hratio, it should now be apparent that the output voltages of sawtoothgenerator 59 and free gyro 63 should be added so that current may beapplied by amplifier 53 to deflection coil 51 proportional to thecomposite image motion and in a direction to thereby oppose said motionso as to freeze the viewed image at the focal plane of camera 44.

Frequently, the hand held camera disclosed in the FIG. 1 embodiment, theterrestrial telescope shown in FIG. 3 and cameras mounted upon variousvehicles such as the cameras disclosed in FIGS. 4 and 5, are slowlypanned; that is their longitudinal axis are angularly rotated to followa moving object for instance, or to view a different portion of theearths surface. In the case of the hand held camera the longitudinalaxis never will be angularly rotated to follow a moving object about 2cycles per second. However, in order to prevent this very low frequencyoscillation from affecting the current in the deflection coils, therebyto displace the entire field of view, a leaky" integrator shown in FIG.6 was developed. In order to prevent integrator circuit 16' fromresponding to the positioning of the camera which would cause gyro 21'to produce frequencies below 2 cycles, resistor 63 is connected in shuntwith the integrating capacitor of integrating circuit 16 as shown inFIG. 6. The value of the resistor is chosen relative to the value of thecapacitor such that the integrator capacitor will not charge up due tocurrents produced by signals applied thereto below 2 cycles a second. Inother words resistor 63 will drain the capacitor to prevent charging atthese frequencies. Where a one microfarad integrating capacitor wasutilized in conjunction with a Philbrick P65 operational amplifier, asatisfactory value of resistor 63 was found to be 500 Ohms.

By the employment of a telescope such as shown in FIG. 2, and by use ofadditional electronic circuitry such as disclosed in FIG. 7, a novelelectronic gun sight and automatic firing control system may befabricated in accordance with the present invention. Cross hairs areprovided within objective 26 or elsewhere in the optical train on thetarget side of the image converter. The telescope is mounted on a weaponsuch as a rifle. In the absence of the aforesaid teachings of thepresent invention the point of intersection of the cross hairs willdance" about the target in response to random motion of the weapon dueeither to body motion of the individual aiming the weapon or due to themovement of a vehicle upon which the individual is being carried. Withthe telescope of FIG. 2, fabricated in accordance with the presentinvention, this dance" will cease and the cross hairs will appearstationary with respect to the target scene since the cross hair imagewill form part of the target image applied to the photo-emissive screenof the image converter. However the longitudinal axis of the rifle boreis still randomly and angularly gyrating about the target axis which maybe described as the straight line between the actual target and thebullet in the bore situated at the firing position. As explained indetail hereinbefore, when the angular deviation of the longitudinal axisof the optical system with respect to the home position is zero in boththe X and Y directions, the integrating amplifiers will produce zerovoltage outputs so that no current flows in the X and Y deflectioncoils, and consequently the image is not shifted about its home positionwithin the image intensifier tube. At some instant during the aforesaidperiod of angular gyration of the longitudinal axis of the bore of theweapon about the target axis, the bore axis and target axis willcoincide and the aforementioned zero voltage conditions at the output ofboth the X and Y integrating amplifiers will occur. In accordance withthe present invention, this condition is virtually instantaneouslysensed electronically, and a sharp pulse is applied to a firing devicesuch as a trigger solenoid. Statistacally speaking, this on target"voltage condition should occur very shortly after the initial citing ofthe target. It is conceivable that this condition could also be sensedby the detection of a lack of magnetic or electric field within theimage intensifier rather than utilizing the zero output voltages at bothof the integrating amplifiers to make this determination.

An optional inhibiting circuit is also provided for preventing theenergization of the trigger solenoid even though the aforesaid zerovoltage conditions are present at the output of both X and Y integratingamplifiers. The inhibition of the actuation of the trigger solenoid willbe produced, unless a miniumum trigger pressure exists upon the trigger,indicating that the individual handling the fire arm is set and doesintend to actually fire the weapon at this time. Additionally, shouldthe angular velocity of the longitudinal axis of the bore be greaterthan a predetermined amount, an inhibit condition is produced whichprevents energization of the trigger solenoid. Where the angularvelocity of the weapon is quite high, it may be seen that by the timethe bullet emerges from the barrel, the bore axis and the target axiswill be slightly but significantly displaced from one another, so thatthe target might be missed, particularly if the target is small; orputting it another way, the bullet direction as it emerges from the borewill be slightly but significantly different from the direction of thebullet axis upon being fired.

The telescope of FIG. 3 is mounted upon a weapon such as a rifle and thecircuitry to be discussed hereinafter is added to the basic system ofFIGS. 1-3.

FIG. 7 discloses the X and Y direction firing circuits together withcircuitry responsive to each firing circuit for actuating a triggersolenoid, which fires the weapon. X direction firing circuit 66 iscoupled to the output circuit of X direction integrating amplifier 16,while Y direction firing circuit 68 is coupled to the outlet circuit ofY direction integrating amplifier 19. The purpose of X and Y directionfiring circuits 66 and 68 is to set the stage for the actuation oftrigger solenoid 71 when the aforementioned zero deflection condition ispresent within the image intensifier 2, thereby to indicate that thelongitudinal bore axis of the weapon is coincident with the target axis.DC trigger amplifiers 67 and 69 may be any amplifiers having the voltagecharacteristics disclosed in FIG. 8. When the output voltage of anintegrating amplifier becomes more positive than point 72, the outputvoltage of the trigger amplifier will sharply rise to a relatively largepositive voltage as shown by the graph. On the other hand, should thenegative voltage produced by the integrating amplifier output exceed thevoltage represented by point 73 of FIG. 8, the output voltage of thetrigger amplifier will go sharply negative as shown. Points 72 and 73are extremely close to the aforesaid zero voltage condition so thatbetween points 72 and 73 the stage will be set for the actuation oftrigger solenoid 71. This type of double trigger amplifier is readilyavailable. Type D-9505 operational amplifier, manufactured by SigneticsIntegrated Circuits of Sunnyvale, California, may be utilized. Ifdesired, twin schmidt triggers may be utilized in place of such anamplifier to obtain the wave form of FIG. 8, as is well known to thoseskilled in the circuit design field.

The electronic circuitry of FIG. 7 is a logic circuit which will, undercertain conditions besides the coincident production of the zero"voltage conditions at the output circuits of the integrating amplifiers,cause energization of trigger solenoid 71.

X and Y direction firing circuits 66 and 68 will cause a mark to beproduced by nand (nor-and) gate 74 upon the simultaneous production ofthe zero voltage condition at the output circuits of the integratingamplifiers which as explained earlier indicate the coincidence of thelongitudinal bore axis of the weapon with the target axis. FIG. 9discloses a table which sets forth the logic performed by each firingcircuit. The ground" trigger amplifier output (72-73) is the firingrange area shown in FIG. 8 and is indicative of the zero output voltagecondition. As shown by the table, a mark (positive) will be produced bynand gate 74 only where the ground or zero" voltage condition issimultaneously present at the trigger amplifier outputs.

A ground condition at the output circuit DC trigger amplifier 67 causesNPN-transistor T-l to assume the conductive or on" condition. As diode76 becomes forward biased so that the voltage at the base of transistorT-l goes positive with respect to the emitter. This ground condition atthe output circuit of trigger amplifier 67 also forward biases diode 77which causes the base of transistor T-2 to go negative with respect tothe emitter, to cause NPN-transistor T-2 to assume the off condition.With T-l in the on" condition, ground (no mark) is applied to the firstinput terminal of nand gate 74. With T-2 off a positive voltage isapplied to inverter 78, which also produces a ground (no mark) conditionat the second input terminal of nand gate 74. Under these conditions,and only under these conditions, a positive mark will be produced at thefirst input terminal of and gate 78 (as nand gate 74 is fully enabled)thereby to partially enable gate 78. In like manner the production of aground or zero voltage at the output terminal of DC trigger amplifier 69causes a positive mark to be produced by Y direction firing circuit 68at the second input terminal of and gate 78, thereby to further enablethis and gate. Excluding for a moment the function of the inhibitterminal of and gate 78, it should now be seen that the simultaneousproduction of zero" voltage conditions at the output circuits of theintegrating amplifiers will cause and gate 78 to be fully enabled,thereby to actuate a one shot multi-vibrator 79, which in turn energizesamplifier 81 to operate trigger solenoid 71. Details of the Y directionfiring circuit 68 have been omitted since this circuit is identical withX direction firing circuit 66. Should a positive voltage output beproduced by trigger amplifier 67 TJ will be turned on and T-2 will alsobe turned on. Under these conditions inverter 78 will cause a positivevoltage to be applied to the second input terminal of nand gate 74, andas a result no mark may be produced by the nand gate at this time andthus and gate 78 is disenabled and trigger solenoid 71 may not beactuated. On the other hand should the output voltage of triggeramplifier 67 be negative, T-l will be off and a positive voltage (mark)is applied to the first input terminal of nand gate 74, thereby toprevent the production of a mark at the output terminal of the nandgate.

FIG. 10 discloses circuitry which inhibits the aforesaid operation whereangular bore velocity exceeds a given predetermined amount in either apositive or negative direction, that is, either swinging from left toright or right to left. When this angular velocity is exceeded in eitherdirection,

it is desired to inhibit the actuation of trigger solenoid 71 since theangular momentum of the bore will cause the bullet to miss the target aspreviously mentioned. X direction rate gyro 21' is shown coupled tophase sensitive detector 23' which are components disclosed in FIG. 2and discussed hereinbefore. It may be recalled that the amplitude of theoutput voltage produced by phase sensitive detector 23 is proportionalto the angular velocity of the bore. The polarity of this voltage isindicative of the direction of the bore; that is swinging right to leftor left to right. Positive clipper 83 and negative clipper 84 arecoupled to the output circuit of phase sensitive detector 23' as shownin FIG. 10. Upon the occurrence at the output circuit of detector 23' ofa positive voltage greater than a predetermined amount, which indicatesan angular velocity above a predetermined amount, a signal will beproduced in the output circuit of positive clipper 83, thereby toactuate one shot multi-vibrator 86, which in turn causes a mark to beproduced at the first input terminal of or gate 87. This mark isforwarded over conductor 88 to the aforesaid inhibit input terminal ofand gate 78, thereby to inhibit the actuation of trigger solenoid 71which might otherwise occur. On the other hand should the output voltageof phase sensitive detector 23' exceed a predetermined amount in thenegative direction, negative clipper 84 will cause the actuation of oneshot multi-vibrator 89, which causes a mark to be produced at the outputterminal of or gate 87, thereby to inhibit and gate 78 to prevent theactuation of trigger solenoid 71.

It will often be desirable to further inhibit the operation of firingcircuits 66 and 68 where an angular velocity on the Y (up-down)direction exceeds a predetermined value. This is accomplished by merelyproviding a second inhibit circuit such as the circuit of FIG. 10,having its input coupled to the Y rate gyro circuit and having itsoutput coupled to inhibit conductor 88.

As in the case of cameras and telescopes, television pick-up devices,etc. we do not wish the panning or slow rotation of positioning of therifle to have any affect upon current flowing through the deflectioncoils of the image converter except during stationary target shooting asexplained hereinafter. We are generally interested in examining thosefrequencies above 1 or 2 cycles per second which represent wobble of therifle bore so that we may hit the target. Accordingly, resistor 91 isconnected in shunt with capacitor 92 as in the panning circuit disclosedin FIG. 6, and discussed hereinabove.

FIG. 1 l discloses an inhibit circuit which may be utilized to inhibitthe enabling of and gate 78 as long as a minimum predetermined triggerpressure is not being applied to trigger 93. In other words if theindividual handling the weapon is not set," although the electroniccircuitry is full enabled, we do not generally wish to actuate thetrigger solenoid. If this inhbit circuit is connected, by closing switch94, for careful studied target shooting, the weapon will not be fireduntil the individual bearing the fire arm is in the set" position. Onthe other hand should the individual bearing the fire arm be engaged injungle warfare or the like, time may be of the essence so that we wouldwant to disenable this inhibit circuit by opening switch 94. Trigger 93is connected to a portion of the rifle frame 96 by means of spring 97.The trigger 93 is actuated in the direction indicated by arrow 98. Astationary contact member 99 is in brushing relationship with a metallicsurface of trigger 93. When trigger 93 is moved in the directionindicated by arrow 98 and a predetermined trigger pressure has beenproduced by spring 97, spring contact 99 is completely uncovered so thatit is no longer in metallic electrical contact with trigger 93. Metallicrifle frame portion 96 has a positive voltage thereon so that a positivemark is produced at the anode of diode 101, to in turn produce apositive mark on inhibit conductor 88 of FIG. 7, as long as contact 99is covered, thereby to inhibit the actuation of trigger solenoid 71.However when the predetermined trigger pressure is exceeded, and contact99 is no longer electrically contacting trigger 93, the positive voltagewhich was previously applied to the anode of diode 101 is removed sothat a mark is no longer applied to and gate 78 to inhibit it. Thus itshould be apparent that when switch 94 is closed, and a predeterminedtrigger pressure has vided to enable the bearer to enable thestablization system upon the weapon coming to rest in the general targetarea, thereby to freeze" the viewed target image. However, for studiedstationary target shooting, it would be undesirable to fire the weaponat this time although the aforesaid zero current (no wobble) conditionsthrough the coils might be present. However, pressure would not yet beexerted on trigger 93 so that the trigger solenoid is disenabled byvirtue of electrical contact 99, as previously explained. The bearer ofthe weapon now causes the cross hairs to be placed directly over thecenter of the target and at this time squeezes the trigger thereby touncover" electrical contact 99 which enables previously inhibited gate78 to in turn enable the firing circuit. Statistically speaking the zerocurrent condition will now be produced in a very short time so that theweapon is fired upon the coincidence of the target axis and the boreaxis as explained in detail hereinbefore.

Just as contact 99 is uncovered, trigger 93 contacts button 100, whichcauses the energization of relay via closed switch 95, to in turndisconnect resistor 91 of both X and Y integrating amplifiers thereby todisenable panning. It is desirable to disenable panning at this timebecause otherwise it is possible for the bore axis to slowly wander ordrift slightly off target and thereafter manifest at a new settlingposition a no wobble" or zero current condition through the X and Ydeflection coils, to in turn fire the weapon. If panning were on, thevoltage produced by the gyros due to the aforesaid low frequency driftwould not be recognized by the R-C circuit of the leakyintegrator-amplifier and thus the weapon might fire and miss the target.With panning off, a charge would be built up in at least one of theintegrating capacitors due to this drift and would prevent the actuationof the fire control circuits as previously explained. Unless and untilthe bore axis is repositioned back to the target axis, this charge wouldnot be removed from the integrating capacitors and the system would notfire. As explained hereinbelow, panning is on when a moving target istracked. Under this condition trigger inhibit switch 94 is opened to inturn open ganged switch 95, thereby to prevent trigger pressure fromdisenabling panning.

A further refinement may be added which allows the bearer of the firearm to pull the trigger all the way back to an extreme position tothereby over-ride all of the aforesaid electronic circuitry and causethe weapon to be manually fired. Such a circuit would merely involve theintroduction of a contact button such as button 99, positioned to becovered by trigger 93 upon the full backward positioned of the trigger,which in turn could complete an electrical circuit to actuate thetrigger solenoid.

If it is desired to fire at a moving target, the aforesaid stablizationswitch is thrown on to effect image stablization in accordance with thepresent invention, while trigger inhibit switch 94 is opened so that thefire control system is fully enabled while the moving target is beingoptically tracked. If inhibit disable switch 94 were not opened, thebearer of the weapon would have to pull the trigger partially back whilefollowing the moving target, which might accidentally cause theaforesaid over-ride firing condition to be met and the weapon would beinadvertently fired. As soon as the aforesaid zero current condition ismet during tracking, the weapon would automatically fire.

FIG. 11 discloses the present invention as utilized in a televisionenvironment. An image orthicon camera tube 102 is disclosed, having aphoto cathode 103 for converting the televised optical scene into anelectron image. Electrons making up the image are accelerated andfocused upon secondary emission target screen 104. The electrons whichare secondarily emitted are collected by collecting screen 106 and theresulting charge variation upon secondary emission target screen 104 issensed by scanning beam 107 which becomes intensity modulated inaccordance with this charge pattern, so that the return beam 108produces a serial video signal train in accordance with the scene beingviewed. All of the foregoing is completely conventional. For a morecomplete discussion and disclosure of an image orthicon tube see page860 of Van Nostrands Scientific Encylcopedia, third edition, 1958. Inaccordance with the present invention two pairs of electron imagedeflecting plates 109 are introduced into tube 102, as shown, therebyprovide means for deflecting the electron image. Each pair of plates iscoupled to an associated gyro circuit of FIG. 2 through an associatedintegrating amplifier; the gyro circuits in turn being affixed to thecamera support case 1 1 1, as shown.

In the absence of deflection plates 109 or equivalent electromagneticyokes, which of course could be utilized in place of the electrostaticdeflection plates, motions of the camera support case would produce theaforementioned image dance at target screen 104. Since the gyro circuitsof FIG. 2 are affixed to camera support case 111, this image dance ormotion is fully compensated for in the same manner as describedhereinabove in connection with the other embodiments of the presentinvention. Of course, a second pair of deflection plates coupled to asecond gyro circuit through a second integrating amplifier are providedbut are not shown in FIG. 11 in order to clarify the figure.

The advantages resulting from the use of the present invention in thevideo field are particularly dramatic where the television cameraequipment is mounted on a moving vehicle such as a helicopter, orautomobile traveling over rough terrain.

Likewise the present invention would be equally applicable to a moviecamera mounted on such a vehicle to thereby stabilize the scene beingphotographed.

The photoemissive screen of the image converter may be coated to producean electron image manifesting a pattern of incident infra red radiation,so that the fire control system embodying the present invention may beutilized for night firing where the target is dimly illuminated. In likemanner telescopic viewing and photographing in accordance with thepresent invention invention may be carried out at night.

While there has been described what is at present considered to be thepreferred embodiment of this invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention and it is, therefore,intended in the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of the invention.

What is claimed is:

l. A fire control system comprising:

a. a weapon having a bore, said bore having a longitudinal axis;

b. viewing means for viewing the image of said target;

c. photosensitive imaging means fixed with respect to said weapon andmovable therewith, for presenting an image of said target to saidviewing means;

d. indicating means for producing signals indicative of the degree ofdisplacement of the longitudinal axis of said bore away from a giventarget axis;

e. deflection means coupled to said indicating means for the imageproduced by said photosensitive imaging means in response to saidsignals indicative of said degree of displacement produced by saidindicating means and in a direction tending to cancel a component ofimage motion caused by the aforesaid motions of said weapon;

f. a firing device; and g. means responsive to said signals from saidindicating means for actuating said firing device when said signalsindicate the lack of displacement of the longitudinal axis of said borefrom said given target axis.

2. Apparatus as set forth in claim 1 wherein said fire control systemincludes means for allowing panning of said weapon at a low frequencywithout said deflection means deflecting the image produced by saidphotosensitive image means to compensate for the low frequency panning.

3. A fire control system comprising:

a. a movable weapon which may be aligned with a target along a giventarget axis;

b. photosensitive target imaging means fixed with respect to saidmovable weapon and movable therewith;

c. sensor means for producing signals indicative of the degree ofdisplacement of said weapon from said given target;

d. deflection means responsive to the production of said indications bysaid sensor means for deflecting the image produced by saidphotosensitive imaging means in a direction tending to cancel imagemotion otherwise caused by motions of said movable weapon away from saidgiven target axis;

. a firing device for firing said weapon; and

actuating means responsive to said signals from said sensor means foractuating said firing device when said signals indicate the lack ofdisplacement of said weapon from said given target axis.

4. The combination as set forth in claim 3 wherein said sensor meansincludes an electrical transducer and said deflection means includesmeans for producing an electrical field having an intensity proportionalto said degree of displacement.

5. The combination as set forth in claim 4 wherein said sensor meansproduces indications of angular displacement of said weapon from saidgiven target axis.

6. The combination as set forth in claim 4 wherein said target imagingmeans includes an image intensifier,

7. The combination as set forth in claim 4 further including triggermeans having a primed state and an unprimed state;

means coupled to said trigger means and responsive to the manifestationof said unprimed state by said trigger means for inhibiting saidactuating means as long as said trigger means remains in said unprimedstate.

8. The combination as set forth in claim 7 wherein said primed state ismanifested as a predetermined minimum trigger pressure.

9. The combination as set forth in claim 4 wherein inhibit means areprovided for inhibiting said actuating means as long as said movableweapon is moving at a velocity greater than a predetermined velocity.

10. The combination as set forth in claim 3 wherein said sensor meansproduces said indications having a frequency of occurrence between N andcycles per second, where N may be any frequency between one and fivecycles per second.

11. The combination as set forth in claim 10 further including means forextending the sensing range of said sensor means to produce indicationshaving frequencies below 100 cycles per second, including indications ofdisplacement of zero to N cycles per second.

12. Apparatus as set forth in claim 3 wherein said fire control systemincludes means for allowing panning of said weapon at a low frequencywithin said deflection means deflecting the image produced by saidphotosensitive target imaging means to compensate for the low frequencypanning.

1. A fire control system comprising: a. a weapon having a bore, saidbore having a longitudinal axis; b. viewing means for viewing the imageof said target; c. photosensitive imaging means fixed with respect tosaid weapon and movable therewith, for presenting an image of saidtarget to said viewing means; d. indicating means for producing signalsindicative of the degree of displacement of the longitudinal axis ofsaid bore away from a given target axis; e. deflection means coupled tosaid indicating means for the image produced by said photosensitiveimaging means in response to said signals indicative of said degree ofdisplacement produced by said indicating means and in a directiontending to cancel a component of image motion caused by the aforesaidmotions of said weapon; f. a firing device; and g. means responsive tosaid signals from said indicating means for actuating said firing devicewhen said signals indicate the lack of displacement of the longitudinalaxis of said bore from said given target axis.
 2. Apparatus as set forthin claim 1 wherein said fire control system includes means for allowingpanning of said weapon at a low frequency without said deflection meansdeflecting the image produced by said photosensitive image means tocompensate for the low frequency panning.
 3. A fire control systemcomprising: a. a movable weapon which may be aligned with a target alonga given target axis; b. photosensitive target imaging means fixed withrespect to said movable weapon and movable therewith; c. sensor meansfor producing signals indicative of the degree of displacement of saidweapon from said given target; d. deflection means responsive to theproduction of said indications by said sensor means for deflecting theimage produced by said photosensitive imaging means in a directiontending to cancel image motion otherwise caused by motions of saidmovable weapon away from said given target axis; e. a firing device forfiring said weapon; and f. actuating means responsive to said signalsfrom said sensor means for actuating said firing device when saidsignals indicate the lack of displacement of said weapon from said giventarget axis.
 4. The combination as set forth in claim 3 wherein saidsensor means includes an electrical transducer and said deflection meansincludes means for producing an electrical field having an intensityproportional to said degree of displacement.
 5. The combination as setforth in claim 4 wherein said sensor means produces indications ofangular displacement of said weapon from said given target axis.
 6. Thecombination as set forth in claim 4 wherein said target imaging meansincludes an image intensifier.
 7. The combination as set forth in claim4 further including trigger means having a primed state and an unprimedstate; means coupled to said trigger means and responsive to themanifestation of said unprimed state by said trigger means forinhibiting said actuating means as long as said trigger means remains insaid unprimed state.
 8. The combination as set forth in claim 7 whereinsaid primed state is manifested as a predetermined minimum triggerpressure.
 9. The combination as set forth in claim 4 wherein inhibitmeans are provided for inhibiting said actuating means as long as saidmovable weapon is moving at a velocity greater than a predeterminedvelocity.
 10. The combination as set forth in claim 3 wherein saidsensor means produces said indications having a frequency of occurrencebetween N and 100 cycles per second, where N may be any frequencybetween one and five cycles per second.
 11. The combination as set forthin claim 10 further including means for extending the sensing range ofsaid sensor means to produce indications having frequencies below 100cycles per second, including indications of displacement of zero to Ncycles per second.
 12. Apparatus as set forth in claim 3 wherein saidfire control system includes means for allowing panning of said weaponat a low frequency within said deflection means deflecting the imageproduced by said photosensitive target imaging means to compensate forthe low frequency panning.